GE b30, Instruction Manual

Page: 531 / 632

CHAPTER 8: APPLICATION OF SETTINGS ZONING AND DYNAMIC BUS REPLICA
B30 BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 8-3
8
Figure 8-2: Approximate CT magnetizing characteristics
8.2 Zoning and dynamic bus replica
8.2.1 Description
The figures in this section show the adopted protection zoning for the two bus sections.
To provide the bus differential zoning as shown in the figures, eight currents need to be measured. Consequently, the
protection cannot be accomplished by one B30. However, as each bus has not more than six connections, two B30s can be
used.
8.2.2 North bus zone
With reference to the following diagram, the North bus differential zone is bounded by the following CTs: CT-1, CT-2 (if S-1
closed), CT-3 (if S-3 closed), CT-4 (if S-5 closed), CT-5 and CT-8. The North bus protection is to operate the following
breakers: B-1, B-2 (if S-1 closed), B-3 (if S-3 closed), B-4 (if S-5 closed), B-5 and B-7.
Consequently, the B30 for the North bus is wired and configured as follows:
•
CT-1 currents are configured as SRC 1 and used as the source 1A of the bus differential zone 1 together with the
FlexLogic “On” constant for the status
• CT-2 currents are configured as SRC 2 and used as the source 1B of the bus differential zone 1 together with the
status of the S-1 switch
• CT-3 currents are configured as SRC 3 and used as the source 1C of the bus differential zone 1 together with the
status of the S-3 switch
• CT-4 currents are configured as SRC 4 and used as the source 1D of the bus differential zone 1 together with the
status of the S-5 switch